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Coastal afforestation suffers from low survival and slow growth due to harsh conditions and lack of robust seedlings. Inoculation of P-solubilizing bacteria (PSB) or N2-fixing bacteria (NFB) are effective in promoting plant growth and thus potentially helpful for coastal afforestation. However, it remains unclear about the generality and specificity of these plant-growth-promoting-bacteria (PGPB) on the growth of salttolerant trees. We inoculated seedlings of two mangrove trees and one terrestrial salt-tolerant tree with pure cultures of PSB or mixed cultures of PSB and NFB. Plant biomass, height, base diameter and N and P concentrations were determined six months after bacterial inoculation. We found that inoculation of PGPB had an overall promoting effect on the seedling growth of three tree species, but the effects differed greatly (3–280% increase) among plant species and bacterial isolates or bacterial combinations. Only in the terrestrial tree, co-inoculations of PSB and NFB showed greater promoting effects than monocultures of PSB. Root: shoot ratios of seedlings were not changed by bacterial inoculation. Inoculation treatments moderately elevated N concentrations in shoots and roots and P concentrations only in roots of seedlings. Our results suggest that PGPB might have a general promoting effect on the seedling growth of salt-tolerant trees. Nevertheless, the magnitude of promoting effects and the comparative advantage of dual inoculation over single inoculation are species-specific. The generality and specificity of the plant-PGPB relationship are similar to the plantmycorrhizal symbiosis. In addition, tissue nutrient improvement might not be the main mechanism of the promoting effects by PGPB.

The extensive production and usage of antibiotics have led to an increasing occurrence of antibiotic residuals in various aquatic compartments, presenting a significant threat to both ecosystem and human health. This study investigated the degradation of selected β-lactam antibiotics (penicillins: ampicillin, penicillin V, and piperacillin; cephalosporin: cephalothin) by UV-254 nm activated H2O2 and S2O82− photochemical processes. The UV irradiation alone resulted in various degrees of direct photolysis of the antibiotics; while the addition of the oxidants improved significantly the removal efficiency. The steady- state radical concentrations were estimated, revealing a non-negligible contribution of hydroxyl radicals in the UV/S2O82− system. Mineralization of the β-lactams could be achieved at high UV fluence, with a slow formation of SO42− and a much lower elimination of total organic carbon (TOC). The transformation mechanisms were also investigated showing the main reaction pathways of hydroxylation (+16 Da) at the aromatic ring and/or the sulfur atom, hydrolysis (+18 Da) at the β-lactam ring and decarboxylation (–44 Da) for the three penicillins. Oxidation of amine group was also observed for ampicillin. This study suggests that UV/H2O2 and UV/S2O82− advanced oxidation processes (AOPs) are capable of degrading β-lactam antibiotics decreasing consequently the antibiotic activity of treated waters.